444
FXUS65 KVEF 140435
AFDVEF

Area Forecast Discussion
National Weather Service Las Vegas NV
935 PM PDT Sat Jul 13 2024

.SYNOPSIS...Another round of scattered thunderstorms is expected
Sunday afternoon. Gusty outflow winds, heavy rain, and frequent
lightning will be the primary threats associated with any storms
that develop. The Eastern Sierra and Southern Great Basin will see
elevated fire weather concerns due to dry fuels and an increased dry
lightning threat. Precipitation chances will decrease each day after
Sunday as moisture retreats to the east. Temperatures will remain 2
to 5 degrees above normal for mid-July through the forecast period.
&&

.UPDATE...Persistent thunderstorms over southern were diminishing in
coverage late this evening and will mostly dissipate by midnight
though isolated showers or storms will be possible overnight mainly
over Lincoln County. Converging flow bewtween the California Coastal
low and the Four Corners high was responsible for the rededeveloping
convection today and this convergence will remain in play through
Sunday as the coastal low lifts toward northern California. So,
another active afternoon of convection is in store for much of our
forecast area and this is reflected in the latest NBM grids with PoP
values of 30-50 percent across Clark, eastern San Bernardino,
Inyo/Esmeralda and Mohave counties. These values have come up a
little from the previous forecast and the grids have been updated
and published with the latest available NBM.
&&


.PREV DISCUSSION...
335 PM PDT Sat Jul 13 2024

.SHORT TERM...Today and Tomorrow.

With a ridge of high pressure positioned over the Four Corners, the
Desert Southwest finds itself in a classic monsoon set up. Southerly
flow aloft has brought anomalous moisture to the region with
precipitable water values increasing from 0.62 inches on Friday
afternoon to 1.14 inches earlier this morning. This anomalous
moisture is already helping to fuel showers and thunderstorms across
our forecast area. Storm have been and will continue to move from
the southeast to northwest throughout the afternoon and evening,
tending to favor areas of higher terrain for development.

Daytime heating and orographic lift will be the primary sources of
lift today with mesoanalysis revealing anywhere from 500 J/kg of
surface based CAPE in across Inyo County and the Southern Great
Basin region to 1,000 J/kg of CAPE across the Mojave Desert. DCAPE
values across our forecast area remain in the 1,500 J/kg to 2,000
J/kg range. These DCAPE values indicate a favorable environment for
the development of strong gusty outflow winds from any storms that
develop. ACARS soundings also point to the outflow wind threat with
an inverted V shape in the lower levels of the atmosphere. This
inverted V shape shows the lack of low level moisture, resulting in
an increased risk of dry lightning for the Southern Great Basin and
Eastern Sierra. As such there is currently a Red Flag Warning in
effect for the aforementioned areas through Sunday evening. Outside
of strong gusty winds and lightning, heavy rain will be the other
threat, especially in the southern and eastern portions of our
forecast area where more moisture is available. While most of these
storms will be moving relatively quickly, isolated floodingwill be
possible in areas with training storms. With daytime heating being
the primary driver of convection, most of the showers and
thunderstorms will begin to dissipate after sunset this evening.

Another round of afternoon showers and thunderstorms is expected
tomorrow. All of this moisture combined with the increased cloud
cover from nearby storms will keep temperatures a few degrees cooler
than they have been. While temperatures will still be 2 to 5 degrees
hotter than normal for mid-July, it will feel like a welcome relief
after the past week of record breaking heat.

.LONG TERM...Monday through Friday.

A ridge of high pressure will continue across the desert southwest
next week. The ridge will be positioned in a place conducive too
push a little moisture northward, but there isn`t a favorable
dynamic situation to have a strong, persistent push. The monsoonal
moisture we do have in place will linger into the beginning of the
work week, mainly over southern portions of the CWA. The chance of
precipitation will be greatest Monday across eastern Mohave County
and the southern Great Basin. Drier conditions can be expected each
day through the week. While temps will remain above normal for much
of the area, conditions will be a bit cooler than we have
experienced over the past week.

&&

.AVIATION...For Harry Reid...Prevailing gusty southeast winds will
transition to a more south to southwest direction but will be highly
dependent on where thunderstorms develop and the strength of any
outflow winds. Convection will continue to develop over the higher
terrain around the Las Vegas Valley with a 40% to 50% chance of at
least one storm moving off the terrain and directly impacting the
airfield after 23z. If storms do not directly affect the airfield,
there is greater than 70% probability of outflow winds from storms
around the valley causing impacts within the terminal area.  Any
thunderstorm development could bring lightning, brief rain, and
sudden erratic gusty winds. Outside of convective activity,
southwest winds can be expected into the early evening. Model
guidance continues to show a brief period of northwest winds after
sunset, but winds should return back to the southwest around
midnight. More thunderstorm activity is possible Sunday afternoon
and evening but with less coverage.

For the rest of southern Nevada, northwest Arizona and southeast
California...Scattered areas of convection will continue to develop
across much of the region through this evening, with storms capable
of producing lightning, brief rain, CIGs to 10kft, and sudden
erratic gusty outflow winds. Storms developing near KDAG this
afternoon have a greater than 60% chance of generating gusty outflow
winds that could spread northward into the Owens Valley during the
late afternoon and evening, possibly reaching KBIH between 00Z and
02Z. Away from areas of convection, south to west winds around 12kts
with gusts to 20kts can be expected. Thunderstorm activity is
expected to diminish after sunset with winds falling below 10kts
across the region overnight. Expect more thunderstorm activity on
Sunday, although there should be less coverage and it will be mainly
over southern Nevada and northwest Arizona.

&&

.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.

&&

$$

SHORT TERM...Stessman
LONG TERM...Berc
AVIATION...Salmen

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